The NA61/SHINE experiment at the CERN SPS is performing a uniqe study of the phase diagram of strongly interacting matter by varying collision energy and nuclear mass number of colliding nuclei. In central Pb+Pb collisions the NA49 experiment found structures in the energy dependence of several observables in the CERN SPS energy range that had been predicted for the transition to a deconfined phase. New measurements of NA61/SHINE find intriguing similarities in p+p interactions for which no deconfinement transition is expected at SPS energies. Possible implications will be discussed.
K+/PI+ at y=0.
K+/PI+ at y=0.
<K+>/<PI+>.
Measurements of multiplicity and transverse momentum fluctuations of charged particles were performed in inelastic p+p interactions at 20, 31, 40, 80 and 158 GeV/c beam momentum. Results for the scaled variance of the multiplicity distribution and for three strongly intensive measures of multiplicity and transverse momentum fluctuations \$\Delta[P_{T},N]\$, \$\Sigma[P_{T},N]\$ and \$\Phi_{p_T}\$ are presented. For the first time the results on fluctuations are fully corrected for experimental biases. The results on multiplicity and transverse momentum fluctuations significantly deviate from expectations for the independent particle production. They also depend on charges of selected hadrons. The string-resonance Monte Carlo models EPOS and UrQMD do not describe the data. The scaled variance of multiplicity fluctuations is significantly higher in inelastic p+p interactions than in central Pb+Pb collisions measured by NA49 at the same energy per nucleon. This is in qualitative disagreement with the predictions of the Wounded Nucleon Model. Within the statistical framework the enhanced multiplicity fluctuations in inelastic p+p interactions can be interpreted as due to event-by-event fluctuations of the fireball energy and/or volume.
Energy dependence of $\Delta[P_{T},N]$ for three charge selections
Energy dependence of $\Delta[P_{T},N]$ for three charge selections
Energy dependence of $\Sigma[P_{T},N]$ for three chrge selections
We present results on transverse momentum ($p_{\rm T}$) and rapidity ($y$) differential production cross sections, mean transverse momentum and mean transverse momentum square of inclusive J/$\psi$ and $\psi(2S)$ at forward rapidity ($2.5<y<4$) as well as $\psi(2S)$-to-J/$\psi$ cross section ratios. These quantities are measured in pp collisions at center of mass energies $\sqrt{s}=5.02$ and 13 TeV with the ALICE detector. Both charmonium states are reconstructed in the dimuon decay channel, using the muon spectrometer. A comprehensive comparison to inclusive charmonium cross sections measured at $\sqrt{s}=2.76$, 7 and 8 TeV is performed. A comparison to non-relativistic quantum chromodynamics and fixed-order next-to-leading logarithm calculations, which describe prompt and non-prompt charmonium production respectively, is also presented. A good description of the data is obtained over the full $p_{\rm T}$ range, provided that both contributions are summed. In particular, it is found that for $p_{\rm T}>15$ GeV/$c$ the non-prompt contribution reaches up to 50% of the total charmonium yield.
Differential production cross sections of $J/\psi$ as a function of $p_{\rm T}$.
Differential production cross sections of $J/\psi$ as a function of rapidity.
Differential production cross sections of $\psi(2S)$ as a function of $p_{\rm T}$.
The $e^+e^-\to K^+K^-$ cross section and charged-kaon electromagnetic form factor are measured in the $e^+e^-$ center-of-mass energy range ($E$) from 2.6 to 8.0 GeV using the initial-state radiation technique with an undetected photon. The study is performed using 469 fb$^{-1}$ of data collected with the BABAR detector at the PEP-II $e^+e^-$ collider at center-of-mass energies near 10.6 GeV. The form factor is found to decrease with energy faster than $1/E^2$, and approaches the asymptotic QCD prediction. Production of the $K^+K^-$ final state through the $J/\psi$ and $\psi(2S)$ intermediate states is observed. The results for the kaon form factor are used together with data from other experiments to perform a model-independent determination of the relative phases between single-photon and strong amplitudes in $J/\psi$ and $\psi(2S)\to K^+K^-$ decays. The values of the branching fractions measured in the reaction $e^+e^- \to K^+K^-$ are shifted relative to their true values due to interference between resonant and nonresonant amplitudes. The values of these shifts are determined to be about $\pm5\%$ for the $J/\psi$ meson and $\pm15\%$ for the $\psi(2S)$ meson.
The $K^+K^-$ invariant-mass interval ($M_{K^+K^-}$), number of selected events ($N_{\rm sig}$) after background subtraction, detection efficiency ($\varepsilon$), ISR luminosity ($L$), measured $e^+e^-\to K^+K^-$ cross section ($\sigma_{K^+K^-}$), and the charged-kaon form factor ($|F_K|$). For the number of events and cross section. For the form factor, we quote the combined uncertainty. For the mass interval 7.5 - 8.0 GeV/$c^2$, the 90$\%$ CL upper limits for the cross section and form factor are listed.
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Axis error includes +- 0.0/0.0 contribution (?////NO DECLAIRED SE.DECAY-BR(BRN=K*(892)+ --> K0 PI+,C=PDG 84)//DECAY-BR(BRN=K2*(1430) --> KAON PION,C=PDG 84)//RES-DEF(RES=K*(892)+,BACK=CORRECTED,DEF=0.72 < M(K0 PI+) < 1.20 GEV,C=M AND W FROM PDG 84)//RES-DEF(RES=K2*(1430)+,BACK=CORRECTED,DEF=1.30 < M(K0 PI+) < 1.68 GEV,C=M AND W FROM PDG 84)//RES-DEF(RES=DEL++,BACK=CORRECTED,DEF= M(P PI+) < 1.6 GEV,C=M AND W FROM PDG 84)).
Axis error includes +- 0.0/0.0 contribution (?////NO DECLAIRED SE.DECAY-BR(BRN=K*(892)+ --> K0 PI+,C=PDG 84)//DECAY-BR(BRN=K2*(1430) --> KAON PION,C=PDG 84)//RES-DEF(RES=K*(892)+,BACK=CORRECTED,DEF=0.72 < M(K0 PI+) < 1.20 GEV,C=M AND W FROM PDG 84)//RES-DEF(RES=K2*(1430)+,BACK=CORRECTED,DEF=1.30 < M(K0 PI+) < 1.68 GEV,C=M AND W FROM PDG 84)//RES-DEF(RES=DEL++,BACK=CORRECTED,DEF= M(P PI+) < 1.6 GEV,C=M AND W FROM PDG 84)).
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New experimental results are presented on inclusive production properties of\(\bar \Sigma ^{ *+ } \)(1385) and\(\bar \Sigma ^{ *+ } \)(1385) inK+p interactions at 32 GeV/c. The analysis is based on significantly larger statistics than previously available. A comparison is also made of invariantx-distributions ofK0/\(\bar K^0 \),\(\bar \Lambda \) and\(\bar \Xi ^ +\) and of\(\bar \Sigma ^{ *\pm } \)(1385) andK*+(892). These spectra exhibit regularities expected from the quark-recombination picture when it is assumed that the strange mesons and antibaryons are produced off the strange\(\bar s\)-valence-quark in the incidentK+ meson. Transverse momentum distributions are also presented forK*+(892) and\(\bar \Sigma ^{ *\pm } \)(1385) and found to be very similar. The results on strange antibaryon average multiplicities disagree strongly with a recent version of the additive quark model.
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The production properties ofKs0,\(\bar \Lambda\) andK+p interactions at 32 GeV/c are investigated using the final statistics of the experiment. We present total and semi-inclusive cross sections and aver-age multiplicities. Estimates are given of the diffractive dissociation contributions to total and differential cross sections. Thex-,pT−, and transverse mass dependence of inclusive and semi-inclusive distributions is discussed as well as properties of “prompt”Ks0's. The ratio of “prompt”K890+ (K8900) to “prompt”K0 cross sections is measured to be 1.03±0.12 (0.98±0.17). From a comparison of\(\bar \Lambda\) production inK±p interactions at 32 GeV/c, we estimate a strange sea-quark suppression of 0.26 ±0.02. The double differential cross sections ofKs0's is studied as a function of Feynman-x andpT2, and a Triple-Regge fit performed. The data are compared in detail to versions of the Lund-model for low-pT hadronic collisions.
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The inclusive production ofK*±(890), ρρ(770), ω0(780) andf0(1,270) mesons is studied in\(\bar pp\) experiment at 32GeV/c in the MIRABELLE bubble chamber by the analysis of (K0π±) and (π+π−) invariant mass distributions. The inclusive cross sections are σ(K*±)=2.45±0.30 mb, σ(ρ0)=8.8 ±0.9 mb, σ(ω+)≃6.2 mb, and σ(f0)=2.2±0.7 mb. The C.M. longitudinal distribution of theK*±(890) is slightly shifted to the primary particles fragmentation regions; the ρ0 is produced more centrally. The studied mesons alone are responsible for 40% of final state poins. The production features of various resonances are compared with quark models predictions.
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